Dog Black Skin Disease (Alopecia X)
"Black skin disease" is not actually a disease, but rather is a phrase used to refer to a form of hormonally-influenced, non-inflammatory, progressive, symmetrical hair loss and skin hyperpigmentation in dogs. The term for this condition preferred by breeders and veterinarians – especially veterinary dermatologists - is "Alopecia X." Alopecia simply means hair loss in areas where it normally is present. A number of other names are used as well, including adrenal sex hormone imbalance, growth hormone responsive alopecia, adult-onset growth hormone deficiency, coat funk, congenital adrenal hyperplasia-like-syndrome, wooly coat syndrome, follicular dysplasia and pseudo-Cushing's disease. Another term is "hair cycle arrest." Alopecia X is a form of patterned baldness, which means that affected dogs lose hair symmetrically on both sides of their body. Typically, hair loss is followed by darkening of the balding skin.
Causes & Prevention
Causes of Black Skin Disease in Dogs
Little is known about this condition or its cause. Factors such as obesity, hormonal imbalances, allergies and genetics have all been suggested as contributors. One theory is that affected dogs have a genetic predisposition to some sort of hormonal imbalance, which somehow affects the function of cells at the level of the hair follicle. Another hypothesis is that there is some inherited defect in the normal hair growth cycle. It may be that Alopecia X is not a single disease at all but rather a combination of several, making diagnosis and treatment that much more difficult.
Preventing Black Skin Disease
Preventing Alopecia X is not realistic at this time, because the cause of the condition is so poorly understood. Certainly, weight management can remove obesity as a contributing factor. Because stress seems to exacerbate the signs of Alopecia X, owners should do their best to remove stressors from their dogs' environment. Castration or spaying, dietary management and other hormonal or environmental management protocols may help to relieve the effects of stress and thereby reduce the hair loss and pigmentation changes associated with this disorder.
Alopecia X does not appear to affect a dog's health. It seems to be a purely cosmetic issue for owners of affected animals, and benign neglect is often the recommended "treatment" of choice. Other conditions can be confused with Alopecia X. Currently, there are no medical tests to definitively diagnose this disorder. A veterinarian must rule out a number of other problems, particularly hypothyroidism and hyperadrenocorticism (Cushing's disease), before concluding that Alopecia X is the cause of symmetrical baldness. This is called making a diagnosis by exclusion.
Symptoms & Signs
"Black skin disease" is a phrase used to refer to a form of hair loss (alopecia) in dogs that seems to be caused or at least influenced by hormonal imbalances. The term more commonly used by veterinarians and breeders for this condition is Alopecia X. Affected dogs typically have normal hair coats as puppies. They begin to develop signs of hair loss and hyperpigmentation (darkened skin) in adolescence to early adulthood, usually by three years of age, although signs may appear at any time. Dogs with this disorder lose their long, outer "guard" hairs first. Most cases start with gradual thinning of hair on the back of the hind legs and along the top of the back. Hair loss also occurs commonly under the tail, on the belly and around the genitals. The soft, fuzzy secondary coat becomes exposed. This is referred to as a "puppy coat" and suggests why Alopecia X is sometimes referred to as "wooly coat syndrome." Over time, even the puppy-coat falls out, leaving the skin bald. The hairless areas tend to spread but normally are not itchy, painful or prone to infection. Darkening of the skin generally follows the hair loss. Some dogs never re-grow their coats; if they do, the hyperpigmented skin usually peels away, exposing fairly normal-looking skin underneath.
Symptoms of Alopecia X - Black Skin Disease in Dogs
Alopecia X is a progressive condition that typically follows a reliable course. This includes:
Gradual loss of color and lushness of the coat (presumably from a loss of melatonin)
Gradual and symmetrical loss of outer guard hairs
Increasingly dry, "cottony" undercoat
Hyperpigmentation of the skin
In extreme cases, hair loss can progress until fur is only present on the dog's head and paws. Normally, the skin discoloration follows the hair loss in patches beginning along the back and hind legs, but in some cases the skin darkens more broadly. The darkening may appear as small flecks of black skin, or the skin may become solid black. Some dogs will re-grow their coat partially or temporarily. No generalized signs of illness are associated with Alopecia X. If your dog has hair loss and also shows changes in appetite or thirst (increased or decreased eating or drinking), acts depressed or shows other signs of systemic illness, there probably is another underlying cause of the alopecia.
Dogs At Increased Risk
Alopecia X has been diagnosed in dogs of all ages and breeds, regardless of their spay/neuter status. However, it seems to occur in males and in certain breeds more frequently than others. Nordic breeds are overrepresented, including the Pomeranian, Chow Chow, Alaskan Malamute, Siberian Husky and Elkhound, among others. Toy and Miniature Poodles are also overrepresented. All coat colors seem to be equally affected.
Diagnosis & Tests
Alopecia X, sometimes called black skin disease, is difficult to diagnose. Many other conditions can be confused with Alopecia X, and currently there is no medical test that can definitively diagnose this condition.
How Alopecia X is Diagnosed
Faced with a dog whose hair is thinning gradually and symmetrically, a veterinarian will want to perform a thorough physical examination and take a detailed history from the owner. Because this condition can mimic so many others, diagnosis can only be made by ruling out other possible causes – called diagnosis by exclusion. Some disorders that can look like Alopecia X include hypothyroidism, hyperadrenocorticism (Cushing's disease), functional tumors of the gonads, infection and/or inflammatory disease of the sebaceous glands (sebaceous adenitis) and other forms of hair follicle dysplasia.
Veterinarians can take a skin biopsy and submit it to a pathology laboratory for analysis. In cases of Alopecia X, the results of this test typically are non-specific and provide little assistance in development of a treatment protocol.
Alopecia X is a cosmetic condition that does not appear to adversely affect a dog's health in any way, other than possibly creating an increased chance of sunburn damage to the exposed areas. Most dogs characteristically retain hair on their heads and legs. Re-growth of hair is highly variable and difficult to predict.
Alopecia X is a form of symmetrical pattern baldness and skin hyperpigmentation seen primarily in Nordic breeds and Toy or Miniature Poodles. While it is purely a cosmetic condition, many owners find it unpleasant to have a progressively balding pet. Treatment protocols for Alopecia X are at best a trial and error approach, since the underlying cause of this disorder is not known. The overall therapeutic goal is to restore the dog's coat and, hopefully, prevent recurrence of hair loss.
Treatment Options for Black Skin Disease
Most hormone-based hair losses look alike. Before treating a dog suspected to have Alopecia X, a veterinarian will try to rule out diseases that mimic Alopecia X, especially Cushing's disease and hypothyroidism. If Alopecia X is caused by hormonal imbalances as is suspected, then hormone therapies can be helpful. The first step in treatment is to spay or neuter intact dogs. There are many health and behavioral benefits to sterilization in addition to helping manage the symptoms of Alopecia X. Many dogs will re-grow most if not all of their coat after they are spayed or neutered because of the hormonal changes associated with those procedures. Unfortunately, hair re-growth is not always permanent.
If the affected dog has been neutered or spayed and several months pass without its coat returning, the veterinarian may recommend oral melatonin therapy as the next treatment step. Melatonin is a nutritional supplement; it is not regulated by the Federal Drug Administration, and there can be significant differences in the amount or quality of melatonin found in different brands. Melatonin is readily available over-the-counter in tablet form at health food stores and vitamin retail outlets, as well as at some supermarkets. Current research suggests that melatonin should be given to dogs with Alopecia X orally for at least two or three months. About 50% of dogs reportedly show improvement in hair growth within 6-8 weeks. Once hair growth has stabilized, if it does, the dose of melatonin typically is gradually tapered to a once-a-week dose. It is possible that the treatment can eventually be discontinued, although hair loss may recur. A veterinarian is the best person to recommend any treatment option, including the appropriate dose of melatonin for an affected dog. Please note that melatonin can cause drowsiness and sedation in dogs and in people. It also can affect diabetes, which underscores the importance of having a veterinarian rule out all other diseases that may be causing the dog's hair loss before classifying the cause as Alopecia X.
If alteration and melatonin do not help, there are some other treatment options to consider. These carry additional potentially adverse side effects and should be discussed with a veterinarian so that the possible benefits of improved cosmetic appearance can be weighed against the possible risks of treatment.
Methyltestosterone therapy (one form of hormone therapy) is often the next treatment option. Testosterone therapy should only be implemented after baseline blood testing, and periodic blood work should be done to monitor levels of this hormone if it is given, as it can be toxic to the liver. This treatment can also cause increased aggression in dogs.
Lysodren, also called mitotane or OP'ddd, is another possible treatment. Lysodren is most often used to treat Cushing's disease (hyperadrenocorticism). Lysodren acts by eroding the outer layers of the adrenal gland, thereby limiting the amount of adrenal hormones made and distributed throughout the body. Lysodren can be helpful in cases of Alopecia X, because the adrenal gland also is responsible for producing sex hormones. Dogs with Alopecia X do not have Cushing's disease, and they do not have an overabundance of corticosteroids. Lysodren can cause abnormally low circulating corticosteroid levels, creating a steroid deficiency known as "Addison's disease," or hypoadrenocorticism. Dogs treated with Lysodren should have regular blood tests to monitor their hormone levels.
Another option involves giving injections of growth hormone, as some authors suggest that Alopecia X may be caused by a deficiency of this hormone. Growth hormone is a genetically engineered product which is difficult to come by commercially but may be available through veterinary or other academic teaching laboratories and institutions. Administration of growth hormone can contribute to diabetes, so the dog's blood sugar levels must be carefully monitored if this treatment approach is used. Reports suggest that a 6-month course of growth hormone therapy may produce good results for several years in dogs with Alopecia X.
Other treatments that have been tried include administration of prednisone, anipryl, ketoconazole, leuprolide, cimetidine and other medications. Essentially, each of the above treatments is an attempt to re-start the hair follicle growth cycle. Obviously, since the exact cause of Alopecia X is unknown, there is no one treatment approach that will work for every affected dog. In cases where the hair loss is mild, shampoos which contain soothing ingredients can help calm the symptoms. Again, owners should consult with a veterinarian about which, if any, treatment protocols are best in any given case.
Very often, the best treatment for Alopecia X is no treatment at all – which in medical jargon is called "benign neglect". While the condition may be unsightly, if it is not harming or bothering the dog, then no treatment is medically necessary. Many dogs with Alopecia X live long, happy lives completely unaffected by their hair loss. They develop their own special look, and are adored by their owners for their uniqueness.